SRD v15 Science-based Requirements

2.5.3 near-InfraRed, Multi-Object Spectrometer (IRMOS)
2.5.3.1 General Description
    This instrument is envisioned to work behind the wide field AO system (MOAO) that delivers individually corrected small fields of view over a large (5 arcmin) field of view. Each deployable AO corrector will then connect to its deployable IFU that will sample the field of view (≤2 arcsec) and feed the spatially divided information into a spectrometer. Each spectrometer may process information from multiple IFU’s depending on the actual instrument design.This instrument is intended to study multiple extended objects. Because they are extended, spatial resolution ~ 0.05 arcsec is anticipated to be typical, depending on the size of the objects, the spatial channels available, and the sampling density desired.  With such coarse sampling, it is expected that the required tip-tilt stability can be relaxed for the AO system.
2.5.3.2 Wavelength Range
    0.8 – 2.5μm
    Discussion: the low density of sources beyond 2.5μm makes coverage beyond 2.5μm unnecessary.
2.5.3.3 Field of View
    IFU heads deployable over 5 arcmin diameter field
2.5.3.4 Image quality
    Should not degrade the image quality delivered by the AO system (50% of energy in 0.050 arcsec)
2.5.3.5 Spatial sampling
    Sampling: 0.05x0.05 arcsec
    IFU head size: 2.0′′ IFU heads
    Number of IFU units: ≥10
    Smallest head separation: as small as practical, no worse than 20 arcsec
2.5.3.6 Spectral Resolution
    R= 2000-10000
    Complete atmospheric band covered in a single exposure at R=4000
2.5.3.7 Throughput
    High throughput is important for this instrument
2.5.3.8 Background
    The instrument should not increase the (inter-OH) background by more than 15% over natural sky (see Appendix 4) + telescope background (assume 5% emissivity at 273K).
2.5.3.9 Detector
    Detector dark current and read noise shall not increase the effective background by more than 5% for an integration time of 2000 s.
Discussion: In the 1-2.5μm region, dark current ≤0.002 e/s and read noise ≤ 2e after multiple reads should be sufficient.